The invention may find use in almost any place where it is necessary to lock a mechanical part in an immobile position until it is safe for that part to move. In particular, the invention is especially useful when size and weight are serious constraints. For example, every ounce that is added to an airplane demands seven or more additional ounces for support, fuel, engine power, etc. Therefore, the inventive safety lock should be as light and as small as it reasonably can be considering the task which it is designed to perform.
However, to give a concrete example of one place where the invention may find special utility, reference may be made to operation of the reverse thrusters on a jet aircraft and to the deployment and retraction of doors behind the jet engine for reverse thrust. For example, when the jet plane is coming in for a landing, many sensors detect things such as weight on the wheels on touch down, the rotational speed of the wheels, and the like. After touchdown, the pilot wants to initiate deployment of thrust reversing doors behind the engine and increase thrust in order to slow the airplane to assist braking on the runway. Also, in the event of a "touch and go" type go around (taking off again after touching down), he wants to be certain that the doors are fully retracted, before he goes to full throttle (forward thrust).
When the pilot moves the levers backward for power with reverse thrust, it is necessary to block movement of the levers until the reverse thrust doors are fully deployed. Otherwise, he might cause power to be applied at a point where the applied force could override the thrust reverse doors and inadvertently apply forward thrust at a critical stage when available runway is running out. Likewise, after the touch down and full deployment of the thrust reverse doors, the pilot might see something on the runway and move to full throttle in order to abort the landing and take off. The full throttle power cannot be allowed to take effect until the thrust reverse doors are stowed. Otherwise, instead of taking off inadvertent reverse thrust would be applied.
Of course, the invention is equally applicable to almost any similar situation where a mechanical part must be restrained from immediate operation, and yet be enabled for an immediate response as soon as it is safe or desirable to do so. One can easily imagine many other examples of situations where a part is locked until sensors of various sorts signal the ability of a mechanical part to move.
In each of these and similar situations, it is necessary to lock the moving part against motions in either of opposite directions of its possible excursion until such motion is safe or desirable. There are many sensors, that respond to such things as the deployment or retraction of the thrust reverse doors, which may be connected to remove the lock upon the movable part as soon as it is safe to do so. The invention should be able to work with most of these sensors.